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Midland Radio SP-300 REMOVING & REPLACING THE BACK COVER

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May 2001

MAXON

SP-300 HAND HELD

REMOVING & REPLACING THE BACK COVER

To remove the Back Cover:

1. Remove battery. (Refer to Removing &Replacing

the Battery)

2. Unscre w the four Back Cover mounting screws

located on the Back Cover of the radio.

3. Remove the Back Cover by pulling the lower battery

bracket away from the radio.

4. The Back Cover can now be removed by pulling the

Back Cover away from the radio chassis. The self

forming gasket ring (A) should remain on the Back

Cover.

To replace the Back Cover:

1. Reverse the steps taken to remove the Back Cover.

ANT CH

VOL

ANT CH

VOL

Figure 9A-Back Cover Removal & Installation

Figure 8B-Back Cover Removal & Installation

Figure 8-Back Cover Removal & Installation

Contents

Main TABLE OF CONTENTS Page SPECIFICATIONS GENERAL TEMPERATURE RANGE CURRENT CONSUMPTION Page RECEIVER Page SP-300 Series HAND HELD INTRODUCTION FEATURES Main Features Wideband Scan Mode Scan Delay Time Busy Channel Lockout Marked Idle Enable Normal/Inverted DCS Standard/Non-Standard CTCSS SP-300 Series HAND HELD VCO Lock Time Low Battery Indication Memory Protect External Option Detect maxon DESCRIPTION OF CONTROLS THEORY OF OPERATION DIGITAL CIRCUITS z RF CIRCUITS RF CIRCUITS PLL SYNTHESIZER RECEIVER Page MAINTENANCE AND REPAIR GENERAL REMOVING & REPLACING THE BELT CLIP REMOVING & REPLACING THE BATTERY REMOVING & REPLACING PTT ASSY. REMOVING & REPLACING THE ACCES- SORY CONNECTOR REMOVING & REPLACING THE ANTENNA & CONTROL KNOBS REMOVING & REPLACING THE BACK COVER REMOVING & REPLACING THE MAIN BOARD z Page REMOVING & REPLACING THE DAUGH- TER BOARDS z REMOVING & REPLACING THE SPEAKER COMPONENT REPLACEMENT z PROGRAMMING ALIGNMENT PROCEDURE z Page -23- TEST EQUIPMENT SETUP 1. S.S.G. : @ 1kHz Audio: 154.625445681125661 ALIGNMENT POINTS DIAGRAM ALIGNMENT POINTS VHF & UHF WITH TCXO MODULE ALIGNMENT POINTS UHF WITH OUT TCXO MODULE Page -25- TROUBLESHOOTING GUIDE Page -26- VOLTAGE CHARTS z z z CONTROL CIRCUIT RX SP-300 HAND HELD z RECEIVE STATE Page -28- TRANSMIT STATE Page -29- SP-300 SERIES UHF & VHF DIGITAL SECTION PARTS LIST Page -30- Page -31- SP-300 SERIES VHF RF SECTION PARTS LIST Page -32- Page -33- Page -34- SP-300 SERIES UHF RF SECTION PARTS LIST Page -35- Page -36- Page Page -38- COMPONENT PINOUT MMBR951 Q16,17,501,601 KRA104S (PD) Q5,410,412 KRA102S (PB) Q1 D405, 406, 407 Page -39- REFERENCE NO. SCHEMATIC D15 D201,202,301 Page -40- PIN DESCRIPTION 1 12 15 RX/TX VCO SCHEMATICS & BLOCK DIAGRAM ues may differ from schematics shown. VHF FRONT-END Schematic P/N: 770-110-0012 Rev. C PCB Assy. P/N: 650-110-0012 Rev C VHF POWER AMP VCO TX VCO R X 97 10 8 13 - 3 1 47K MMBR9426 PAGE -44- May 2001 Digital Schematic PTT SCHEMATIC P/N:480-042-0028 DESCRIPTIONDESCRIPTIONREV ARELEASED TO MANUFACTURING DGC 5/01 SP-300 Series Digital Schematic Diagram VHF RF Schematic AUDIO AMP DESCRIPTIONDESCRIPTIONREV VCO RX SECTION FUSE SCHEMATIC P/N: 650-200-0004 PAGE -46- May 2001 UHF RF Schematic P.A. MODULE(UHF) SCHEMATIC P/N: 650-230-0013 VCO TX SECTION (UHF) P/N: 650-030-0020 VCO RX SECTION FRONT-END (UHF) SCHEMATIC P/N: 650-110-0013 FUSE SCHEMATIC P/N: 650-200-0004 Block Diagram REVISIONS NA DESCRIPTIONDESCRIPTION RELEASED TO MANUFACTURING REV A PCB LAYOUTS TCXO1 VR3 J3 Board Layout (Top) Main Board Assembly 416121B Exploded View SEE NOTE 3 SEE NOTE 1 SEE NOTE 2